Open gear lubricants containing silicones



OPENGEAR-LUBRICANTS CONTAINING SILICONES Lorne W. Sproule. and Thomas M. Rogers, Samia, Ontario, Canada, assignors to Esso Research and Engineering "company, a corporation 'of, Delaware This invention relates to lubricating compositions and more particularly relate'sfto open gear lubricants of a grease consistency containing silicone compositions,

which lubricants have'long lubrication lives.

.In thegprior art, lubricants designed for heavy-duty service, for example for heavy and relativelylarge and rough open-type gears, have commonly consisted of viscous mineral lubricating, bases of a grease consistency either eloneorcompounded with additive materials, such as fatty acid soaps, sulfonates and the like. Such lubricants when employed in open-type gears are exposed to the atmosphere, and because of this exposure the lubrication life of such gear lubricants has been relatively limited. 7 s

It has now been .found that the addition of relatively high concentrations, -at least about 0.05% by weight, of certain silicone compositionstothese types oflubricants substantially increases *theirflubrication life. 'By incorporating these silicone compositions at relatively high concentrations in such lubricants in accordance with this invention, it has been foundthat the lubrication life of the lubricants, bothin the presence of and the absence of water, is greatly improved. Although silicones have been added to normally'liquid lubricating oil compositions heretofore, they have been "added in substantially lower concentrations, generally 'lessthan about 0.01%, and for a different purpose, namely, to reducefoaming of the liquid oil compositions. Thisfoaming problem does not exist with the viscous mineral, lubricating bases used in the present -'compositions -as-the compositions of necessity arenon-fluid at gear operating temperatures to thereby prevent loss of the lubricant fromthe open gears as well as to provide proper lubrication.

. The gear lubricant compositions of this inventionare lubricants having :a grease consistency which comprise a major proportion of a'viscous mineral lubricating base and a minor, but lubricating life extending proportion, of a non-fluid silicone composition consisting essentially of a fluid dimethyl silicone polymer thickened with a small amount of finely divided silica. In addition to the viscous mineral lubricating base and the silicone composition, the gear lubricant compositions of this invention may contain conventional gear lubricant additives such as fatty acid soaps, sulfonates, and the like. Thegear lubricants may be :blended with a volatile solvent to reduce the viscosity of the lubricant compositions so that the lubricant compositions may be more easily applied to open gears.

. The silicone compositions useful in this'invention .con-

:sist essentially of a mixture of'a .dimethyl siliconepoly- .mer having an S.U.S. viscosity at 210 F.fin therange of about 300 to 3,000 thickened with about 4.0 to 20.0 wt. percent (based on the silicone composition) of finely divided silica. The dimethyl silicone polymers have the following. general formula:

where Rreprsents a methyl (CH group and x is an integersuflicient to provide apolymer having the-aforementioned viscosity. Preferred silicone compositions consist essentially of .-a .dimethyl silicone polymer having an S.U.S. "viscosity'at 210 F. in the range of about "5.00 to 2,000 thickened with about *8 to 12 wt. percent of finely divided silica. It will be understood of course that mixtures of dimethyl silicone polymers of difiie'rent molecular weights may be employed in gpreparing'the aforedescribed silicone compositions. The -finely divided silica used as the thickener is preferably an amorphous substantially anhydrous SiO having an ultimate particle size of about Sto 100 millimicrons, forexarnple 10 to -50 millimicrons. The preparation :of these silicone poly- .mers is well known to the'art and is'described for example in detail in the book Chemistry of silicones by Eugene 1G. Rochow.

The viscous mineral lubricating bases useful in this invention are those having. agreaseconsistency which are preferably derived from petroleum crude oils having .a high asphalt and/or-resin content. The viscosity-ofth'e viscous mineral lubricating base should'be'about 1;000 to.6,000-and:preferab1yabout1,500 to 5,000 -S.S.U. at

The preferred viscous mineral lubricating *base is one which contains .ahigh asphalt-content. particular type of'lubricant'base is wellknownin the'art-andzmay .be obtained from ,natural asphalts suehlas natural Trinidad, Bermudez, gilsonit'e, :grahamite and Cuban or may :beobtained from --an asphaltic gpetroleum crude 'oil,

such as 'those' of .South'America, 'California or Mid- Continent crudes,.-by -removing the lighter fractions from the crudeoil. The removalof ithese'lighter :fractions frorrra petroleum crude oilmaybeaccomplished by welllknown methods, iiforiexample, by steam distillation, by

vaciuum flashing in .pipe stills, or :by solvent separation.

Steamdistillation is carried out by treating a crude oil "residuum, remaining after atmospheric distillation of light Si0CkS,*Wilh steam sprays .to removeadditional light stocks, thereby producing a concentrated asphalt v residuurn. Vacuum flashingiin pipe stills is .a moreefli- .cient method for removing the light stocks from crude oil residua than is isteam distillation as it may'be carried out under vacuumat alower temperature and'thus prevents degradation of the products of this operation. Suitable viscous mineral-lubricating bases may be also .obtained bytsolvent separation ofthe asphalt contentof crude residua from the light stock content. This method, which'is also well known in the art, is accomplished by employing a light hydrocarbon solvent such as butane and propane. bases may be prepared by blending'products of difierent viscosities, obtainedby one or more of the above three mentioned-methods, to therebypreparea viscous mineral lubricating b'ase of a desired viscosity. The asphaltic residua obtained by any of the above methods maybe oxidizedwithair to produce lubricating bases having improved properties. AlsO, if desired, a heavy asphalt=residua or natural asphalt'may' be cut back or blended asphalt residua-in order topreparea mineral lubricating Also, suitable viscous mineral lubricating which contains a substantial proportion of the resinous constituent. Certain crude oils may contain a substantial proportion of both asphalt and resin constituents and they may likewise be used in this invention.

Generally, therefore, the viscous mineral lubricating bases of this invention which have a grease consistency are preferably petroleum residua of high asphalt and/or res-in content obtained by the removal of the light stocks from a crude oil by such means as distillation, solvent separation and the like. In certain applications, the viscons mineral lubricating bases may be combined with tars or pitchessuch as wood tar, coal tar, vegetable pitch, and the like, if desired.

The viscous mineral lubricating base represents a major proportion of the lubricant composition of this invention. Preferably, it will represent about 80.00 to 99.95% by weight of the total lubricant composition. The silicone compositions of this invention are utilized in proportions suflicient to extend the lubrication life of the gear lubricant. More specifically, they should be employed at a concentration in the range of about 0.05 to 3.0% by weight, and preferably at a concentration in the range of about 0.08 to 1.5% by weight, based on the total lubricant composition; In addition to the viscous mineral lubricating bases and the silicone compositions described above, it will be understood that various conventional additive materials may be also incorporated into the lubricants of this invention as will be apparent to those skilled in the art. Thus, anti-oxidants such as phenyl alpha naphthylamine, rust inhibitors such as oilsoluble sodium petroleum sulfonates or other similaralkali or alkaline earth sulfonates, tackiness agents, extreme pressure agents such as lead oleate, sulfurized fatty oils, etc., film-forming agents such as colloidal graphite and the like, may be added for particular purposes without departing from the spirit of the present invention.

The silicone compositions and other additives, if any, may be simply incorporated into the viscous mineral lubricating base by mixing. The total lubricant composition should be of a grease consistency and should have an S.S.U. viscosity at 210 F. in the range of about 1,000 to 6,000 and the ingredients should be selected to formulate such a composition.

Since the lubricants of this invention are non-fluid and relatively viscous, it is preferred to blend them, especially the higher viscosity lubricants, with a volatile solvent such as trichlorethylene, carbon tetrachloride, naphtha, etc. so that they may be readily applied to open gears. A non-flammable volatile solvent is preferred. After a relatively short period of time (e.g. 4-5 hours at 100 F.), the volatile solvent evaporates, leaving the lubricant compositions of this invention adhering as a film to the open gears. By employing such volatile solvents, the necessity of heating such compositions prior to their application to open-gears is eliminated. The amount added to the lubricant compositions of this invention should be sufiicient to produce a semi-fluid composition, generally about 5 to 30% by weight based on the total solvent-free composition. Particularly preferred compositions containing a volatile solvent include a viscous mineral lubricating base having a viscosity in the range of about 1500 to 5000 S.S.U. at 210 F., trichlorethylene, colloidal graphite and a silicone compo sition of this invention. These preferred compositions have the following formulation:

LUBRICANT COMPOSITION 1 Weight percent (based on Ingredient the total solvent-free composition) Viscous mineral lubricating base (1,500- About to 95.

5,000 SSU at 210 F.). Trichlorethyleue (solvent)...,, About 5 to 30. Colloidal graphite About 5 to 15. Silicone composition About 0.08 to 1.5.

1 Composition may also include minor amounts of conventional gear lubricant additives.

The following examples of this invention arepre- The lubrication life of a viscous mineral lubricating base was determined both in the presence and absence of water. The mineral lubricating base, which will hereinafter be termed Lubricating Base 1, consisted essentially of South American (Tia Juana) reduced asphaltic crude oil having an S.S.U. viscosity of about 2,000 at 210 F. and a softening point of about F. LubricatingBase I was evaliiated in the following lubricant life test:

The lubricant was applied to open gears operating at a temperature of 100 F., carrying a load of 260 lbs. per tooth, and operating at a peripheral speed of 134 ft. per minute. A zenith pump driven through a variable speed transmission was used to drip water on the gear at a given rate. The lubricant life was arbitrarily chosen as the pointwhen a /2 bare area on the bearing surface was visible when viewed under ultra-violet light.

The following results were obtained when evaluating the lubricant life of Lubricating Base I in the abovedescribed lubricant life test:

Table I LUBRICANT LIFE or LUBRIOA'IING BASE 1 Water (Jon- Lubricantv tact Rate Lire (hrs) (ca/min.)

Table II LUBRICANT LIFE OF LUBRICATING BASE I PLUS CONVENTIONAL ADDITIVES Additive Water Oon- Lubricant Additive Concentact Rate Lire Gus.)

tration 1 (ce./min.)

Olelc acid 5. 0 30 15 Castor oil 5. 0 30 15 Pine tar 15. 0 30 15 Barium sulfonate..- 10. 0 30 12 Calcium acetate 20. 0 30 4 1 Weight percent, based on total composition.

attests It will be noted that none of the aboveconventional agents or additives were efiective;in:,increasing the lubricant life of- Lubricating Base I in the presence of water. In fact several of the conventional additives actuallly. reduced the, lubricant life.

A non-fluid silicone composition of. the present invention was then evaluated as a lubricating life. extending agent in. Lubricating Base 1'. This, silicone composition, which will hereinafter be referred to as Additive A, consisted essentially ofdimethyl siliconepolymer having an S.U.S. viscosity at210 F. of about 1234 seconds (S.U.S. viscosity at 100 F. wasabout 3100 seconds) thickened with about percent (based ontotal silicone composition) of finely divided silica (having a particle size in the range of about 10m 50 millimicrons), For-comparison purposes, a fluid dimethyl silicone polymer(not containing any finely divided silica) having an S.U.S. lviscosity at 100 F. of about 350 seconds, hereinafter referred to as Additive B, was also evaluated. The following results were observed in the aforedescribed lubricant life test:

Table III LUBRICANT LIFE OF LUBRICATINGEBASE I PLUS SILICONE ADDITIVES It will be noted that Additive A was extremely effective in increasing the lubricant life of Lubricating Base 1. More specifically, the addition of only 0.1% by weight of Additive A approximatley doubled the life of Lubricating Oil Base I when employing 30 cc. per minute water contact rate. It will also be noted that Additive A had even a greater effect in increasing lubricant life under dry operating conditions, the increase amounting to about 250%. On the other hand, Additive B had no effect on the lubricant life of Lubricating Base I even though utilized at a concentration of 2 wt. percent.

EXAMPLE 2 The viscous mineral lubricating base utilized in this example was essentially a South American (Tia Juana) reduced asphaltic crude oil having an S.U.S. viscosity of about 5,000 at 210 F. This viscous mineral lubrieating base, hereinafter referred to as Lubricating Base H, was cut bac with trichlorethylene to give a composition (Composition 1) consistingessentially of about 90% by weight of Lubricating Base II and about 10% by weight of trichlorethylene. Composition 1 which had a Saybolt Furol viscosity at 130 F. of about l000'se'conds was evaluated in the aforedescribed lubricant life test. A second composition (Composition H) was also evaluated in this example. The second composition consisted of 89.9% by weight of Composition I (i.e. 90 wt. percent of Lubricating Base II and 10 Wt. percent of trichlorethylene) blended with 0.1% by weight of Additive A (described in Example 1) and 10% by weight of colloidal graphite. The colloidal graphite had essentially no thickening power and hence did not interfere with the gear life.

The following results were obtained with" thesetwo lubricant compositions:

Tabl'e W V LUBRICANT LIFE OF LUBRIOATING" BASE II WITH' AND WITHOUT SILICONE ADDED-IVES Qoncen Water 0on- Lubricant. Composition tretion of tact Rate: Life (hrs.)

' Additive A (eel/min) I None 0 l 75 I None 30 15 II 0.1" 0 185 II 0:1" 1 3D. 26

Weight percent, based on total composition (including volatile solvent).

It will be noted that, the addition of 0.1%, of the silicone composition of this invention, Additive A, substantially increased both the wet and dry life of Lubricating Base II.

having an S.U.S. viscosity at 210 F. in the range of about 300 to 3,000, and (2) in the range of about 4.0 to 20.0 wt. percent, based on the silicone composition, of finelydivided silica.

2. A gear lubricant composition according to claim 1 wherein said viscous mineral lubricating base is a reduced asphaltic petroleum crude oil.

3. A gear lubricant composition according to claim admixed with a volatile solvent.

' 4. A gear lubricant composition having a grease consistency consisting essentially of a major proportion of a viscous asphaltic mineral lubricating base having an S.U.S. viscosity at 210 F. in the range of about 1,500 to 5,000 and in the range of about 0.08 to 1.5 by weight, based on the total composition, of a silicone composition consisting essentially of (1) dimethyl silicone polymer having an S.U.S. viscosity at 210 F. in the range of about 500 to 2,000, and (2) in the range of about 8.0 to 12.0 wt. percent, based on the silicone composition, of finelydivided silica.

5. A gear lubricant composition consisting essentially of a major proportion of a viscous mineral lubricating base having an S.U.S. viscosity at 210 F. in the range of about 1,000 to 6,000, in the range of about 5 to 30% by Weight, based on the total solvent-free composition of a volatile solvent, and in the range of about 0.05 to 1.5 by weight based on the total solvent-free composition of a silicone composition consisting essentially of a (1) dimethyl silicone polymer having an S.U.S. viscosity Weight percent (based on Ingredient the total solvent-free composition) Viscous mineral lubricating base About to 95. Trichlorethylene (solvent) About 5 to 30. Colloidal graphite About 5 to 15 Silicone composition About 0.08 to 1.5.

wherein said lubricating base has an S.U.S. viscosity at 210 F. in the range of about 1500 to 5000 and said silicone composition consists essentially of (1) dimethyl silicone polymer having an S.U.S. viscosity at 210 F. in the range of about 500 to 2,000 and (2) in the range of about 8.0 to 12.0 wt. percent, based on said silicone composition, of finely-divided silica.

9. A gear lubricant composition consisting essentially of a reduced asphaltic petroleum crude oil having an S.U.S. viscosity at 210 F. in the range of about 1,500 to 5,000 and in the range of about 0 .08 to 1. 5% by weight based on the total composition of a silicone composition consisting essentially of (1) dimethyl silicone polymer having an S.U.S. viscosity at 210 F. in the range of about 500 to 2,000 and (2) in the range of about 8.0 to 12.0 wt. percent, based on said silicone composition, of finelydivided silica.

References Cited in the file of this patent UNITED STATES PATENTS f 2,428,608 Baas 061.7, 1947 2,466,927 Burton Apr. 12, 1949 2,508,596 Cox May 25, 1950 2,645,588 Barry July 14, 1953 2,677,658 Bidaud May 4, 1954 2,756,212 Hotten July 24, '1956 FOREIGN PATENTS 715,592 Great Britain Sept. l5, 1954 OTHER. REFERENCES "Lubricating Greases, by Boner (1954), pp. 921-22 and 795-99, Reinhold Pub. Co., New York, NY. 

1. A GEAR LUBRICANT COMPOSITION HAVING A GREASE CONSISTENCY CONSISTING ESSENTIALLY OF A MAJOR PROPORTION OF A VISCOUS MINERAL LUBRICATIG BASE HAVING AN S.U.S. VISCOSITY AT 210*F. IN THE RANGE OF ABOUT 1,000 TO 6,00, AND IN THE RANGE OF ABOUT 0.05 TO 1.5% BY WEIGHT, BASED ON THE TOTAL LUBRICANT COMPOSITION, OF A SILICONE COMPOSITION CONSISTING ESSENTIALLY OF (1) DIMETHYL SILICONE POLYMER HAVING AN S.U.S. VISCOSITY AT 210*F. IN THE RANGE OF ABOUT 300 TO 3,000 AND (2) IN THE RANGE OF ABOUT 4.0 TO 20.0 WT. PERCENT, BASED ON THE SILICONE COMPOSITION, OF FINELYDIVIDED SILICA. 